Power-operated handheld dehiders are well known in the meat processing industry. Generally speaking, these tools have oppositely reciprocating cutting blades, usually disk-shaped with serrated outer edges. The adjacent cutting disks are driven in opposite cutting oscillations, typically by a pair of oscillating pushrods connected to an eccentric drive mechanism driven by an air motor carried on the tool. As the pushrods oscillate, the teeth on one rotary disk move past the teeth on the oppositely-moving rotary disk. This produces a shearing and cutting action that separates the hide from the carcass.
Although this dehider design has proved effective in the industry for many years, various improvements have been developed over time to address certain problems that have arisen from using these dehiders. Among these problems are the noise and vibration caused by using the tool over prolonged periods of time on a production line. The oscillating nature of the eccentric-driven pushrods and the cutting blades produces substantial vibration. And excessive vibration of these handheld dehiders as well as other handheld power tools can lead to workplace hazards such as hand-arm vibration syndrome, such as carpal tunnel syndrome. These problems have been recently addressed by OSHA standards to protect workers from the ill effects of constantly using handheld vibrating power tools such as eccentric-driven dehiders.
To reduce vibration experienced with oscillating dehiders, recent design approaches have been taken. These include reducing the weight of the tool and/or counterbalancing the moving mass of the pushrods, as examples. As for dehiders in particular, the oscillating blades are driven at high speeds during use, typically at speeds in excess of 6,500 strokes per minute (“spm”). The tool tends to slow down when pressure is applied and can return to a much higher no-load speed when the cutting load is released. The no-load speed can momentarily return to at least 8,000 spm, for example. This causes worker fatigue as well as excessive vibration forces being transmitted from the handheld device. Attempts to reduce vibration have also included motor speed controls and speed governors to smooth out the accelerations that cause undue vibrations which otherwise occur during normal changes in load applied by the cutting blades during use. Examples of such speed controls are disclosed in U.S. Pat. No. 7,722,448 to Gwyther and U.S. Pat. No. 4,901,400 to Karubian.
Thus, there is an ongoing need to produce a handheld dehider that is light in weight and is essentially devoid of vibration problems caused during normal use over extended periods of time. The tool should also maintain standard cutting efficiencies and be easy to repair and operate at a reasonable cost.